Abstract 4785: Identification of HSP105 as a novel non-Hodgkin lymphoma (NHL) restricted antigen

Abstract

Abstract We recently reported that vaccination using dendritic cells (DCs) loaded with killed autologous tumor cells in relapsed indolent NHL patients induced objective clinical responses that correlate with multifaceted immunological responses. In particular, since responders (R) showed tumor-restricted humoral immunity in autologous setting, we exploited antibody (Ab) repertoires from vaccinated patients to evaluate whether the observed antibody responses was directed to indolent NHL-shared antigens (ags). Immunohistochemistry and flow-cytometric analyses of biotinylated Immunoglobulins (Igs) from vaccinated patients’ serum samples preadsorbed on normal isolated B cells in the attempt to decrease Abs cross-reacting with normal auto-ags showed that only post-vaccine serum Ig of responders specifically reacted with higher intensity on allogeneic NHL tumors (either long term cell cultures or primary tumors from the same series) compared to matched biotinylated Igs from control samples (pre-vaccine serum from responders, pre- and post-vaccine serum from non-responders and healthy donors). In addition, only Abs contained in post-vaccine serum from R significantly inhibited NHL DOHH2 cells growth strongly suggesting the presence of therapeutic Abs in their serum samples. These findings indicate that Igs from R recognize tumor cell-surface associated molecules different from patient-specific idiotypes and support the potential expression of novel NHL-restricted ags. As a step toward identifying NHL-restricted ags as potential novel therapeutic targets, we applied a properly modified serological proteome analysis (SERPA) using as target DOHH2 cells and as probes pre- and post-vaccine Ab repertoires from our series. Proteins, fractionated using an OFFGEL IPG strip (pH 3-10), were separated on SDS-PAGE and then immunoblotted with pre- and post-vaccine Igs from R and controls. Differential hybridization analyses have revealed some potential candidate tumor-associated antigens which include heat shock protein 105 (HSP105), whose immunological role has been already proved in solid tumors. Preliminary data indicate that HSP105 is also expressed on cell membrane from different tumor B cell lines and experiments are in progress to evaluate its potential implication in tumor growth control. Partially supported by AIRC. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4785.